Install help on sony vaio e series vpceh28fn needed

Install help on sony vaio e series vpceh28fn needed

I was trying to install Ubuntu 12.4 LTS on Sony Vaio e series vpceh28fn
laptop. I've been using Ubuntu for 2 years and I've done at least 12
installations, usually I press F11 and select my live USB and run Ubuntu.
But on this laptop it booted Windows 7 directly. Is there any way I can
access the boot menu, because I've just had to restore windows from a
crash and I'd not like to go though that again.
specs:
Intel multi core i5-2430m processor 2.40ghz
windows 7 première (64bit)
4gb ram
500gb hard disk